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Diesel engines as power sources ranging in size from small to large have been extensively used worldwide. However, further improvement in the complicated urea-SCR systems is required to meet the stricter NOx regulations on exhaust gas. This study shows that the behavior of the entire gas/injected droplet can be verified using visualization equipment. Valuable gas-liquid multiphase flow PIV results using the DDM were obtained. In addition, the detachment droplet behavior from the liquid film was visualized as unknown droplet behavior. These validations are considered to be useful for establishing the PIV-DDM for the flow characteristic estimation in the exhaust pipe of the urea-SCR system.

This study was visualized by experimental and numerical analysis for the unknown injected droplet phenomena with the multi-phase flow in the Urea-SCR dosing system. Visualization experiments were conducted on the droplet behavior inside the pipe with simulated urea SCR injection system. Although the total number of droplets decreases at gas temperatures of 150°C and 200°C, a significant number of injected droplets remained at the position corresponding to the SCR catalyst. That is physical kinetic energy was found to dominate over thermal evaporation. However, the impingement of droplets into the pipe wall had occurred complex behavior by physical/thermal evaporation, and these droplets weren't on gas airflow at the lower part of the pipe. Furthermore, these actual phenomena were reflected in experimental coefficients for new reduction model analysis instead of CFD.